MECHANICAL-PROPERTIES OF NEUTRON-IRRADIATED CERAMIC MATERIALS

A comprehensive discussion is given on strength changes in ceramic materials under neutron irradiation. It is mainly based on KfK measurements on different types or grades of Al2O3 and SiC, but also includes some MgAl2O4 and AlN results. Volume and crystal lattice changes are considered for the explanation of the irradiation effects. The comparatively small reduction of Young's modulus is correlated with the volume increase under irradiation. The decrease in fracture strength becomes considerable at about 5 x 10(24) n/m(2). At elevated temperatures the strength decrease is probably due to the formation of irradiation defect aggregates in Al2O3, but a different defect type seems to be responsible in SiC. Additional measurements of the fracture toughness change showed that there is no conclusive correlation with the fracture strength. The strength reduction under irradiation has to be explained mainly by facilitation of the crack initiation process, except at rather low temperatures.